Hard challenge
Best choice for me is mono piranas, 5 staple cards are super cheap and used in 90% of monodecks: puff tula ector taljion coleridge (less than 2.5k all ).
11 stars to fill with 2.5k, u can try kristin sheryl tyd/morgane, or if u want to play a 5* use sliman and play 5-3-3.

If u prefer biclan consider ulu and roots, u can make a decent deck without spending a lot